# US 2018/0026684 A1 · Dmrs enhancement for higher order mu-mimo

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- Number: US 2018/0026684 A1
- Document ID: US20180026684A1
- Status: Published application
- Kind: A1
- Application number: 15/549,597
- Filed: 2016-02-09
- Published: 2018-01-25
- Earliest claimed: 2015-02-10
- Assignees: QUALCOMM Incorporated
- Applicants: Qualcomm Incorporated
- Inventors: Chao WEI; Wanshi CHEN; Peter GAAL; Guodong LI; Jilei HOU
- Web page: https://patentgrep.com/patent/US20180026684A1

## CPC

- H04B 7/0452: Multi-user MIMO systems
- H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
- H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT}
- H04L 5/0021: {in which codes are applied as a frequency-domain sequences, e.g. MC-CDMA}
- H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)}
- H04L 25/0242: {using matrix methods}
- H04W 72/0453: Resources in frequency domain, e.g. a carrier in FDMA
- H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

Certain aspects of the present disclosure support demodulation reference signal (DMRS) enhancement for higher order multi-user multiple-input multiple-output (MU-MIMO) communications. An example method generally includes determining a plurality of ports of a multi-dimensional array of transmit antennas and a number of spatial multiplexed layers for transmission to a plurality of user equipments (UEs), configuring a demodulation reference signal (DMRS) pattern by multiplexing the layers or the ports in the DMRS pattern, using an orthogonal cover code (OCC) and one or more code division multiplexing (CDM) groups, and transmitting DMRS symbols based on the configured DMRS pattern using the multiplexed layers and the ports.

## Claims

### Claim 1

A method for wireless communications by a base station (BS), comprising:
determining a plurality of ports of a multi-dimensional array of transmit antennas and a number of spatial multiplexed layers for transmission to a plurality of user equipments (UEs);
configuring a demodulation reference signal (DMRS) pattern by multiplexing the layers or the ports in the DMRS pattern, using an orthogonal cover code (OCC) and one or more code division multiplexing (CDM) groups; and
transmitting DMRS symbols based on the configured DMRS pattern using the multiplexed layers and the ports.

### Claim 2 (depends on 1)

The method of claim 1, wherein:
the OCC comprises a length-2 OCC;
the one or more CDM groups comprise a first CDM group allocated to a first pair of layers or a first pair of ports, and a second CDM group allocated to a second pair of layers or a second pair of ports;
the first CDM group and the second CDM group are non-orthogonally multiplexed on same resource elements in time and frequency domain; and
the first CDM group uses a different scrambling sequence than the second CDM group.

### Claim 3 (depends on 1)

The method of claim 1, wherein:
the OCC comprises a length-2 OCC;
the one or more CDM groups comprise a first CDM group allocated to a first pair of layers or a first pair of ports, and a second CDM group allocated to a second pair of layers or a second pair of ports; and
orthogonal time division multiplexing (TDM) and frequency division multiplexing (FDM) is applied between the first CDM group and the second CDM group

### Claim 4 (depends on 1)

The method of claim 1, wherein:
the OCC comprises a length-4 OCC, and
the one or more CDM groups comprise a single CDM group allocated to four layers or four ports spanning four noncontiguous resource elements (REs) in time domain.

### Claim 5 (depends on 1)

The method of claim 1, wherein:
the OCC comprises a length-4 OCC,
the one or more CDM groups comprise:
a first CDM group allocated to a first set of tour layers or four ports spanning four noncontiguous resource elements (REs) in time domain, and
a second CDM group allocated to a second set of four layers or four ports spanning the four noncontiguous REs in time domain; and
the first CDM group and second CDM group are non-orthogonal multiplexed on same resource elements in time and frequency domain, wherein the first CDM group uses a first scrambling sequence and the second CDM group uses a second scrambling sequence.

### Claim 6

The method of claim f, further
providing, to the plurality of UEs, an indication about the configured DMRS pattern using radio resource control (RRC) signaling.

### Claim 7 (depends on 6)

The method of claim 6, wherein the indication comprises:
first data indicating a type of multiplexing used for a first and a second CDM group; and
second data indicating a length of the OCC.

### Claim 8 (depends on 1)

The method of claim 1, further comprising:
dynamically switching the configured DMRS pattern based on a speed of a user equipment (UE) of the plurality of UEs or capability of the UE to support higher order multi-user multiple-input multiple-output (MU-MIMO) communications.

### Claim 9 (depends on 1)

The method of claim 1, further comprising:
communicating indication about the ports of the multi-dimensional array of transmit antennas and the number of layers for transmitting the DMRS symbols using L1 control signaling on a Physical Downlink Control Channel (PDCCH).

### Claim 10 (depends on 1)

The method of claim 1, further comprising:
communicating joint indication of the configured DMRS pattern and the ports of the multi-dimensional array of transmit antennas using L1 control signaling.

### Claim 11 (depends on 10)

The method of claim 10, wherein:
the joint indication comprises one bit for Physical Downlink Shared Channel (PDSCH) rate matching indication and four bits indicating the configured DMRS pattern and the ports of the multi-dimensional array of transmit antennas.

### Claim 12 (depends on 1)

The method of claim 1, wherein:
the OCC comprises a length-4 Walsh code indicated by the sequence {a, b, c, d}, and the method further comprises
switching, on the frequency domain, between the OCC and another OCC, wherein the other OCC is a cyclic shift version of the length-4 Walsh code.

### Claim 13 (depends on 12)

The method of claim 12, wherein the other OCC comprises a length-4 Walsh code indicated by the sequence {b, c, d, a}.

### Claim 14 (depends on 1)

The method of claim 1, further comprising:
scheduling UEs of the plurality of UEs for a plurality of bundled resource blocks (RBs) used for transmitting the DMRS symbols;
applying the same precoder to the plurality of bundled RBs; and
providing, to the co-scheduled UEs, indication about a size of the plurality of bundled RBs.

### Claim 15

An apparatus for wireless communications by an eNodeB, comprising:
at least one processor configured to:
determine a plurality of ports of a multi-dimensional array of transmit antennas and a number of spatial multiplexed layers for transmission to a plurality of user equipments (UEs); and
configure a demodulation reference signal (DMRS) pattern by multiplexing the layers or the ports in the DMRS pattern, using an orthogonal cover code (OCC) and one or more code division multiplexing (CDM) groups; and
a transceiver configured to:
transmit DMRS symbols based on the configured DMRS pattern using the multiplexed layers and the ports.

### Claim 16

A method for wireless communications by a user equipment (UE), comprising:
receiving, from a base station (BS), a downlink (DL) control signaling indicative of a demodulation reference signal (DMRS) pattern;
determining, based on the DL control signaling, ports of a multi-dimensional array of antennas and spatial multiplexed layers for DMRS symbols transmission, the ports and the layers being multiplexed in the orthogonal DMRS pattern using an orthogonal cover code (OCC) and one or more code division multiplexing (CDM) groups; and
receiving the DMRS symbols based on the determination.

### Claim 17 (depends on 16)

The method of claim 16, wherein:
the OCC comprises a length-2 OCC;
the one or more CDM groups comprise a first CDM group allocated to a first pair of layers or a first pair of ports, and a second CDM group allocated to a second pair of layers or a second pair of ports;
the first CDM group and the second CDM group are non-orthogonal multiplexed on same resource elements in time and frequency domain; and
the first CDM group uses a first scrambling sequence and the second CDM group uses a second scrambling sequence.

### Claim 18 (depends on 16)

The method of claim 16, wherein:
the OCC comprises a length-2 OCC;
the one or more CDM groups comprise a first CDM group allocated to a first pair of layers or a first pair of ports, and a second CDM group allocated to a second pair of layers or a second pair of ports; and
orthogonal time division multiplexing (TDM) and frequency division multiplexing (FDM) is applied between the first CDM group and the second CDM group

### Claim 19 (depends on 16)

The method of claim 16, wherein:
the OCC comprises a length-4 OCC, and
the one or more CDM groups comprise a single CDM group allocated to four layers or four ports spanning four noncontiguous resource elements (REs) in time domain.

### Claim 20 (depends on 16)

The method of claim 16, wherein:
the OCC comprises a length-4 OCC,
the one or more CDM groups comprise:
a first CDM group allocated to a first set of four layers or four ports spanning four noncontiguous resource elements (REs) in time domain, and
a second CDM group allocated to a second set of four layers or four ports spanning the four noncontiguous REs in time domain; and
the first CDM group and second CDM group are non-orthogonal multiplexed on same resource elements in time and frequency domain, wherein the first CDM group uses a first scrambling sequence and the second CDM group uses a second scrambling sequence.

### Claim 21 (depends on 16)

The method of claim 16, further comprising:
receiving an indication about the DMRS pattern via radio resource control (RRC) signaling.

### Claim 22 (depends on 21)

The method of claim 21, wherein the indication comprises:
first data identifying a type of multiplexing used for a first and a second CDM group; and
second data identifying a length of the OCC.

### Claim 23 (depends on 16)

The method of claim 16, further comprising:
receiving an indication about the ports of the multi-dimensional array of antennas and the number of layers for transmitting the DMRS symbols using L1 control signaling on a Physical Downlink Control Channel (PDCCH).

### Claim 24 (depends on 16)

The method of claim 16, further comprising:
receiving joint indication of the DMRS pattern and the ports of the multi-dimensional array of antennas using L1 control signaling.

### Claim 25 (depends on 16)

The method of claim 16, wherein:
the joint indication comprises one bit for Physical Downlink Shared Channel (PDSCH) rate matching indication and four bits indicating the configured DMRS pattern and the ports of the multi-dimensional array of transmit antennas.

### Claim 26 (depends on 16)

The method of claim 16, further comprising:
processing, based on the same bundling boundary for co-scheduled user equipments (UEs), the DMRS symbols received within a plurality of bundled resource blocks (RBs),
wherein the same precoder was used for each port within the plurality of bundled RBs.

### Claim 27 (depends on 16)

The method of claim 16, further comprising:
processing, based on a higher layer configured bundling boundary, the DMRS symbols received in a plurality of bundled resource blocks (RBs),
wherein the same precoder was used for each port within the plurality of bundled RBs.

### Claim 28

An apparatus for wireless communications by a user equipment (UE), comprising:
a processor configured to:
determine, based on DL control signaling, ports of a multi-dimensional array of antennas and spatial multiplexed layers for DMRS symbols transmission, the ports and the layers being multiplexed in the orthogonal DMRS pattern using an orthogonal cover code (OCC) and one or more code division multiplexing (CDM) groups; and
a transceiver configured to:
receive, from a base station, the downlink (DL) control signaling indicating a demodulation reference signal (DMRS) pattern, and
receive the DMRS symbols based on the determination